1. Field of the Invention
The present invention relates to a pressure relief safety valve for use on hydraulic jacks or supports in mines.
2. Description of the Prior Art
In mining operations, it is known that a hydraulic chock includes strut jacks that are wedged between the ceiling and the walls of the galleries. These jacks apply a significant pressure while sustaining the pressure applied by the adjacent beds.
The latter, however, may increase and reach practically unlimited values. It is, therefore, necessary to make provisions for a pressure relief safety valve, called "slide control valve", on the hydraulic systems of the supports.
Some slide control valves are already known, such as the one described in French Pat. No. 2 504 974 for instance. This type of slide control valve may encompass several variations by providing the slide control safety valve with different spring return means, such as a metal spring, a gas cushion, or a stacking of spring washers. The aforementioned assembly requires a relatively large valve.
The present invention eliminates these disadvantages by offering a slide control hydraulic pressure relief safety valve designed with a spring return means including a compressed gas cushion whose construction offers both a limited number of components and reduced overall dimensions.